利用热扩式边材液流探针（TDP）测定树木整株蒸腾耗水量的研究

 介绍了热扩散式液流探针的工作原理及利用液流探针测定树木边材液流速率的方法。利用边材液流探针和多种气象因子传感器及数据采集系统组成的微型气象站，通过对北京西山地区油松(Pinus tabulaeformis)、栓皮栎(Quercus variabilis)混交林林分平均木树干边材液流速率及风速、有效辐射和空气温度、空气相对湿度的日变化和连日变化的测定和分析，揭示了5月干旱季节两树种蒸腾耗水的日变化和连日变化规律，以及栓皮栎树干基部和树冠大枝边材液流的差异，并进行了理论推导，同时分析了液流速率的波动规律与主要气象因素波动的相关性。

MEASUREMENT OF WHOLE TREE'S WATER CONSUMPTION WITH THERMAL DISSIPATION SAP FLOW PROBE (TDP)

Traditional singletree water consumption acquired by means of the scaling-up method from leaflet transpiration measurement, caused serious deviation to the very value. The whole tree water consumption by crown transpiration is closely approximated to the same of sap flow rate in the trunk sapwood which was measured by thermal dissipation probe (TDP) implanted in the trunk. The forest community water consumption can be acquired by scaling-up of singletree water consumption. Spatial-and-temporal sap flow velocity (SFV) fluctuation in the sapwood at lower and upper trunk position of Quercus variabilis and Pinus tabulaeformis, and other meteorological factors, such as solar radiation intensity, air humidity, air temperature, wind speed and soil temperature were measured in a 48 year-old mixed stand at an east hill slope, in the Forest Research Station of Beijing Forestry University in the West Mountains of Beijing (N 39°54′, E 116°28′) in May, 2001. The main elements of sap flow ascending force were transpiration pulling tension (which was determined by crown transpiration) and capillary tension (which was determined by the capillary diameter). Patterns of daily and diurnal SFV fluctuation of the two tree species were quite different. Diurnal SFV fluctuation of Q. variabilis appeared “ascend promptly in the morning (5:30 -10:00 am) and get the peak in the afternoon （13:00-16:00）, then descend slowly and reach the valley during the night”. SFV in upper trunk of Q. variabilis was much higher than that in the lower trunk, and the peak and valley appearing time in the upper trunk were much more early than that in the lower trunk, too. SFV and its rhythm of P. tabulaeformis were different to that of Q. varaibilis during the measuring season with the daily crest appeared in the early morning (4:20-8:00) and went down to the valley in the mid-day (11:00-14: 20). Daily SFV peak height of P. tabulaeformis was only one fourth of Q. variabilis. Fluctuation of solar radiation intensity, air temperature, and air humidity appeared a similar rhythm to the SFV of Q. variabilis, and indicated that there was a close relation between SFV and the meteorological factors. Problems existed in the SFV measurements were discussed in this paper.